1. Field of the Invention
The present invention relates to a fiber unwinding device, and more specifically to a device that minimizes average tension levels and tension variations of a plurality of elastomeric fibers being transported to a downstream fiber processing operation.
2. Description of Background Art
The most common method of unwinding fiber from a cylindrical mandrel (or xe2x80x9cpackagexe2x80x9d) in manufacturing processes is referred to as xe2x80x9crolling takeoffxe2x80x9d. When the package is exhausted the empty mandrel must be removed and a new package installed. This operation requires shutting down the manufacturing line causing unproductive downtime.
Another method often utilized, the over end takeoff (OETO) method, allows continuous operation, because the terminating end of the fiber wound on an active package can be attached to the leading end of the fiber wound on a standby package. This allows the active package to be fully exhausted at which point the standby package becomes the active package, all without any process interruption. However, unacceptable variations in threadline tension are common with OETO.
Research Disclosure, p. 729, November 1995, item #37922, discloses an OETO system in which elastomeric fiber is passed through a system comprising a relaxation section and motor driven nip rolls, before being fed to the manufacturing line. The relaxation section, extending between the package and the nip rolls, is stated to suppress tension variations. However, fibers that exhibit high cohesive forces (generally referred to as xe2x80x9ctackxe2x80x9d) display unusually high variations in frictional forces and tension levels as the package unwinds. The slackness of the thread line in the relaxation region can vary and can result in temporarily excessive amounts of filament being unwound from the package. This excess fiber can be drawn into the nip rolls and wound up on itself leading to entanglement or breakage of the threadline requiring the manufacturing line to be stopped. The high level of tack contributes to the possibility of the excess fiber adhering to itself and to the nip rolls. The OETO device can also be configured such that the fiber horizontally traverses the relaxation section. In this case, the fiber then travels through nip rolls whose axes are vertical. However, in this configuration, the fiber in the region between the package and the nip rolls can sag. This sagging allows the threadline position on the nip rolls to become unstable and can result in interference between adjacent threadlines.
U.S. Pat. Nos. 3,797,767; 3,999,715 and 6,158,689 disclose the use of spirally grooved rolls in fiber winding machines in order to impart a specified pitch angle to a fiber as it is wound on a package. The use of grooved rolls for maintaining positional stability among a plurality of thread lines on a single roll is not described.
The aforementioned problems make the processing of high tack, elastomeric fibers particularly problematic. Fiber tack and its associated problems have been addressed by using topical fiber additives (prior to winding) or by unwinding the package and re-winding it on a new mandrel. However, both approaches add additional expense. Furthermore some applications (such as diaper manufacturing) require the use of as-spun fiber that is substantially finish-free and, consequently, exhibits high tack.
A fast and reliable method of removing high tack elastomeric fiber from a package is still needed.